It is not surprising that Guido Reinking, of Germany, would defend diesel cars against hybrids ("Marketing, not logic, drives demand for hybrids," Comment, Oct. 8). But at least in the case of the Toyota Prius, the facts run counter to his argument.

Using the EPA's Web site, www.epa.gov, one can determine the fuel economy and relative greenhouse gas emissions of various cars. According to the EPA data, the 2008 Prius has a combined fuel economy of 46 mpg and a relative greenhouse gas index of 10, the best rating. The diesel Mercedes-Benz E320 Bluetec (classified by the EPA as a mid-sized car like the Prius) offers only 27 mpg combined economy and a greenhouse gas rating of 7.

While there are more diesel cars available in Europe, according to similar data from the British government, the Prius still comes out above the diesel offerings.

It is true that some hybrids have been sold on hype alone, without the corresponding performance to back it up. But those cars have never gained mass appeal. Toyota sells the Prius not solely on marketing hype but by hitting the sweet spot between economy, performance and size quite nicely.